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Having a peculiar issue (exception raised despite being valid) when
defining a decorator that takes a class method as a callback. Here is a
cooked example:
def decorator( callback ):
 def inner(func):
 def application( *args, **kwargs ):
 callback(*args,**kwargs)
 func(*args,**kwargs)
 return application
 return inner
class DecorateMe:
 @decorator( callback=DecorateMe.callback )
 def youBet( self ):
 pass
 def callback( self ):
 print "Hello!"
>>> DecorateMe().youBet()
Traceback (most recent call last):
 File "<pyshell#0>", line 1, in <module>
 DecorateMe().youBet()
 File "C:\Python25\badpython.py", line 4, in application
 callback(*args,**kwargs)
TypeError: unbound method callback() must be called with DecorateMe
instance as first argument (got DecorateMe instance instead)
If you change the line "callback=DecorateMe.callback" to
"callback=lambda x: DecorateMe.callback(x)" python gives you:
>>> DecorateMe().youBet()
Hello!
Mysteriously, I did encounter this during my coding with a non-cooked
decorator.

First, your code does not compile: when compiling the DecorateMe class
body, the DecorateMe class does not yet exist, and
"callback=DecorateMe.callback" is an error!
And this explains your surprise: certainly there is a previous version
of a DecorateMe class in your module (or interactive session). This
other class has the same name, but it is still a different class, hence
the message.